This invention relates to a method, employing an assembly, for manufacturing clad metal plates, particularly clad steel plates to provide steel plates having a corrosion resistant surface.
For background information relating to the subject of this disclosure, reference should be had to U.S. Pat. No. 4,790,471 that issued Dec. 13, 1988 entitled "Method of Cladding Tubing and Plate Products" and U.S. Pat. No. 4,869,422 that issued Sep. 26, 1989 entitled "Subassembly For Use In Manufacturing A Clad Steel Plate". These previously issued United States patents are incorporated herein by reference. For additional background information relating to the subject matter of this patent application, the United States and Japanese patents cited in U.S. Pat. Nos. 4,790,471 and 4,869,422 are helpful.
This invention is concerned with an improved method of manufacturing clad metal plate products. While the invention is not so limited, it is typically employed in manufacturing steel plates having bonded on one surface a corrosion resistant alloy. For most industrial applications the clad plate is formed by a relatively thick carbon steel substrate that has metallically bonded to it, on one surface, a thin plate of corrosion resistant alloy, such as a nickel base alloy or stainless steel. However, the substrate can be metal plates other than carbon steel and the corrosion resistant alloy other than a nickel alloy or stainless steel. For example, such corrosion resistant alloy may be of a titanium or zirconium base. At the present time, the most important commercial application of the invention is for manufacturing a carbon steel plate having on one surface a nickel based or stainless steel corrosion resistant clad. This product is used for pipes, vessels or other chambers that contain corrosive liquids or gases and is applicable for use in many circumstances where economy, high strength and reliable corrosion resistance are required.
As is pointed out in U.S. Pat. Nos. 4,790,471 and 4,869,422, before the disclosure of the content of such patents, the manufacture of clad plating products in the United States and other countries of the world was performed by cleaning and pickling the base plate and the cladding plate. In this process one faying surface of the base plate and/or cladding plate usually is coated by electrolytic nickel plating. The two plates are assembled together and, at very high pressures and temperatures, and employing high reduction ratios, the plates are hot rolled. This method requires high temperatures and extremely high rolling pressures in order to obtain a metallic forge bond between the base plate and the cladding plate. The nickel plating is used as a diffusion barrier. This technique frequently results in contamination of the cladding plate by carbon from the substrate and formation of brittle carbides at the interface. Further, the finished product has low bond strength.
The new concept provided in U.S. Pat. Nos. 4,790,471 and 4,869,422 have dramatically improved the manufacture of clad plating. The present invention is an advancement of the state of the art represented by U.S. Pat. Nos. 4,790,471 and 4,869,422 and provides a method, employing an assembly, to substantially increase the speed, quality and efficiency of production of clad metal plate products.